MUSEUM OF COMPAKATIVE ZOOLOGY. 51 



This little shell T at first supposed to be the young of the preceding species, 

 but a careful examination of many specimens has shown that this is not the case, 

 and there is no evidence to indicate immaturity. The close resemblance in 

 the other characters leads to the supposition that it is related to Callogaza, of 

 which until more is known it will form a subdivision. 



Microgaza rotella n. s. 



Shell depressed, with five whorls, somewhat flattened above and below ; nu- 

 cleus small, translucent white, and with the two first whorls polished, smooth 

 or marked oidy by faint growth-lines ; remainder of the whorls with a nar- 

 row puckered band revolving immediately below the suture, on which the 

 shell matter is as it were pinched up into slight, elevations at regular intervals, 

 about half a millimeter apart. In some specimens, outside of this band an im- 

 pressed line revolves with the shell ; remainder smooth, shining or with eva- 

 nescent traces of revolving lines impressed from within and strongest about the 

 rounded periphery ; base rounded toward the umbilical carina over which it 

 seems to be drawn into flexuously radiating well-marked plications (about 

 thirty-two on the last turn) which disappear a third of the way toward the 

 periphery ; walls of the umbilicus concave, overhung by the carina, turns of 

 the shell so coiled that the part of each whorl uncovered by its successor forms 

 a narrow spiral plane ascending to the apex like a spiral staircase or screw 

 thread. Pillar straight, thin, with no callus ; aperture rounded except at the 

 angle of the umbilical carina ; margin thin, sharp, not reflected or thickened ; 

 no callus on the body whorl in the aperture ; shell whitish or greenish ; nacre 

 less brilliant in dead or deep-water specimens ; with zigzag brown lines vari- 

 ously transversely disposed and disappearing on the base. Alt. 4.0. Maj. diam. 

 6.75 ; of umbilicus, 1.75 ; of aperture, 2.5 mm. 



Station 2, 805 fms. Barbados, 100 fms., etc. 



The coloration recalls that of some species of Cyclotus. 



FLUXINA n. g. 



Shell porcellanous, depressed conical, umbilicate, strongly carinate. with a 

 stout umbilical rib, above which the pillar is thin and emarginate ; from the 

 umbilical rib to the carina the basal margin of the aperture is deeply flexu- 

 ously emarginate ; above the carina it is again but less deeply emarginate, 

 then sweeps forward roundly and then slightly recedes before joining the pre- 

 ceding whorl. 



This curious form belongs in all probability to the SotariAdai roprcnc n t ing 

 among them Basffissa among the Trochida, and recalling Platytchisma, but 

 witli a different aperture. When perfect the margin at the carina must project 

 forward like a claw, or nail, as in Sch&xostoma. When adult, the nuclear whorls 

 are filled up with a solid deposit of shelly matter, and it is probable that there 

 is a slight notch at the end of the umbilical rib. 



